Heavy rain in the Mississippi Valley is prompting the U.S. Army Corps of Engineers to open the Bonnet Carré Spillway on Friday, April 11 at noon for the first time in 11 years.
The Corps will open the spillway to keep the volume of Mississippi River flows at New Orleans from exceeding 1.25 million cubic feet per second (cfs), which current projections indicate will occur on April 11, 2008. The spillway may be open for an estimated two to four week period, during which time the Mississippi is expected to crest at about 17 feet at New Orleans, without operation of the spillway.
Operation of the structure will relieve pressure on local levees, lower river stages, and reduce the velocity of the river current from the spillway southward.
The decision to open Bonnet Carré is the responsibility of Mississippi River Commission President Brig. Gen. Michael J. Walsh, commander of the Corps’ Mississippi Valley Division in Vicksburg, Miss.
Environmental, hydrologic, structural, navigational and legal considerations all bear on the decision to open Bonnet Carré. Essentially, the spillway is only operated when existing conditions, combined with predicted discharges, reach the operational level as prescribed in the approved Bonnet Carré Spillway Operations Manual and the Mississippi Valley Division Operations Plan 2007-02 for Floods.
Other factors that affect the decision are the overall condition of the levees and the ability of the river to pass flows, and the effects high water and river currents may have on vessels navigating the river, including the risk of vessels losing control and colliding with levees.
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